linux-kernel - Re: [PATCH v2 3/3] rust: alloc: make `ReallocFunc::call` inline

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Message-ID: <Z3z-0xLgUvPcVTO8@pollux>
Date: Tue, 7 Jan 2025 11:15:47 +0100
From: Danilo Krummrich <dakr@...nel.org>
To: Gary Guo <gary@...yguo.net>
Cc: Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>,
	Boqun Feng <boqun.feng@...il.com>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <benno.lossin@...ton.me>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	rust-for-linux@...r.kernel.org, llvm@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/3] rust: alloc: make `ReallocFunc::call` inline

On Sun, Jan 05, 2025 at 07:40:06PM +0000, Gary Guo wrote:
> This function can be called with different function pointers when
> different allocator (e.g. Kmalloc, Vmalloc, KVmalloc), however since
> this function is not polymorphic, only one instance is generated,
> and function pointers are used. Given that this function is called
> for any Rust-side allocation/deallocation, performance matters a lot,
> so making this function inlineable.
> 
> This is discovered when doing helper inlining work, since it's discovered
> that even with helpers inlined, rust_helper_ symbols are still present
> in final vmlinux binary, and it turns out this function is inhibiting
> the inlining, and introducing indirect function calls.
> 
> Signed-off-by: Gary Guo <gary@...yguo.net>

Acked-by: Danilo Krummrich <dakr@...nel.org>

> ---
>  rust/kernel/alloc/allocator.rs | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs
> index 439985e29fbc..aa2dfa9dca4c 100644
> --- a/rust/kernel/alloc/allocator.rs
> +++ b/rust/kernel/alloc/allocator.rs
> @@ -80,6 +80,7 @@ impl ReallocFunc {
>      /// This method has the same guarantees as `Allocator::realloc`. Additionally
>      /// - it accepts any pointer to a valid memory allocation allocated by this function.
>      /// - memory allocated by this function remains valid until it is passed to this function.
> +    #[inline]
>      unsafe fn call(
>          &self,
>          ptr: Option<NonNull<u8>>,
> -- 
> 2.47.0
>